Research activities on magneto-optical devices in Japan

Recent research and development on magneto-optical materials and devices in Japan are reviewed. Investigations on the growth of Bi-substituted iron garnet bulk crystals and films are extensively carried out, and high-quality and compact isolators for
1.3 \sim 1.6 \mu
m and 0.8 μm regions are realized. Large temperature coefficient of Faraday rotation for Bi garnets becomes an actual problem. It is improved by using a combination of Bi garnet and rare-earth garnet with different signs for the temperature coefficient. As for other devices, magneto-optical switches and magnetic field (current) sensors are noted in view of the applications to optical communication and control systems. Basic researches on waveguide-type magnetooptical devices are in progress. It is shown that growth-induced birefringence found in LPE-grown Bi garnet films is effective to achieve phase matching between TE and TM modes in a planar waveguide. In addition to conventional microfabrication techniques, new techniques such as laser annealing and laser etching will be available to develop integrated magnetooptical devices in near future.